Lawrence Ward - Academia.edu (original) (raw)

Papers by Lawrence Ward

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Advances in Neuroelectric and Neuromagnetic Methods, 2009

Dyslexia, 2021

We examined the brain networks and oscillatory dynamics, inferred from EEG recordings during a wo... more We examined the brain networks and oscillatory dynamics, inferred from EEG recordings during a word-reading task, of a group of children in grades 4 and 5 (ages 9–11), some of whom were dyslexic. We did this in order to characterize the differences in these dynamics between typical and dyslexic readers, and to begin to characterize the effect of a phonological intervention on those differences. Dyslexic readers were recorded both before and after they participated in a FastForWord (FFW) reading training program for approximately six months and typical readers were recorded once during this period. Before FFW dyslexic readers showed (i) a bottleneck in letter recognition areas, (ii) expansion in activity and connectivity into the right hemisphere not seen in typical readers, and (iii) greater engagement of higher-level language areas, even for consonant string stimuli. After FFW, dyslexic readers evinced a significant reduction in the engagement of language processing areas, and more...

Mathematical Biosciences and Engineering, 2019

Scientific Reports

this study attempts to answer the question: "is hearing the last to go?" We present evidence of h... more this study attempts to answer the question: "is hearing the last to go?" We present evidence of hearing among unresponsive actively dying hospice patients. Individual ERP (MMN, P3a, and P3b) responses to deviations in auditory patterns are reported for conscious young, healthy control participants, as well as for hospice patients, both when the latter were conscious, and again when they became unresponsive to their environment. Whereas the MMN (and perhaps too the P3a) is considered an automatic response to auditory irregularities, the P3b is associated with conscious detection of oddball targets. All control participants, and most responsive hospice patients, evidenced a "local" effect (either a MMN, a P3a, or both) and some a "global" effect (P3b) to deviations in tone, or deviations in auditory pattern. importantly, most unresponsive patients showed evidence of MMn responses to tone changes, and some showed a P3a or P3b response to either tone or pattern changes. Thus, their auditory systems were responding similarly to those of young, healthy controls just hours from end of life. Hearing may indeed be one of the last senses to lose function as humans die. In the last hours before an expected natural death many people enter a period of unresponsiveness, during which they no longer respond to their external environment. This can be a profound and spiritual time for families, but it is currently unknown whether unresponsive patients are aware of the touch or words of their loved ones. There is a persistent belief, however, that some unresponsive patients may still be aware of touch and sound 1 , despite being unable to reliably signal their awareness. Much of this belief comes from reports of near-death experiences (NDEs), where a common recurring element of this experience is hearing unusual noises or hearing oneself pronounced dead 2-4. Reports from NDEs, however, are difficult to interpret, because incidence of NDEs is low, between 6% 5 and 12% 6 of cardiac arrest survivors, and the cognitive neuroscience underlying NDEs remains hotly debated 7-9 and poorly understood 10-12. Further perpetuating the belief that "hearing is the last to go" are some family members and health care providers who have reported that unresponsive patients will occasionally groan or make a small facial movement in response to hearing a familiar voice, but to our knowledge there is no empirical evidence to corroborate these anecdotes 13. is it possible for a dying brain to sustain awareness? Neuroprotective mechanisms, mainly the blood-brain barrier, reduce neuronal firing in response to ischemia (a common physiological cause of unresponsiveness at the end of life), which could protect the brain from irreversible brain damage under these conditions 14. The brain's tolerance to ischemia has been demonstrated in autopsy, as only about 60% of patients who had been declared brain dead before death showed signs of moderate to severe cortical ischemia, and only about 30% in deep brain structures such as the thalamus and basal ganglia, and a similar percentage in the cerebellum 15 (see also the following responses 16,17). The brain, therefore, may be somewhat resistant to the effects of ischemic damage while the rest of the body shuts down just before death. In addition, opioids can reduce behavioural responses to external stimulation, without necessarily reducing awareness 18. Pain and shortness of breath are common symptoms among the physiological changes that occur at the end of life 19-21 , and are frequently controlled with opioids 22-24. Patients who are being treated for pain with opioid medications could, therefore, become less responsive to their external environment as they enter the final stage of dying, but may retain some covert awareness. Finally, a surge of cortical gamma power and connectivity is present in the rat brain for 30 seconds immediately following cardiac arrest 25 (see also the following response 26). Because synchronous gamma oscillations have been linked to conscious cognitive processing in humans 27-31 , increased gamma synchrony could generate an NDE immediately after cardiac arrest (this interpretation is, however, debated) 26. Although these studies point to the potential for awareness in the dying brain, they speak to neurophysiological

Physical Review E

A diffusion-type coupling operator biologically significant in neuroscience is a difference of Ga... more A diffusion-type coupling operator biologically significant in neuroscience is a difference of Gaussian functions (Mexican Hat operator) used as a spatial-convolution kernel. We are interested in pattern formation by stochastic neural field equations, a class of space-time stochastic differential-integral equations using the Mexican Hat kernel. We explore, quantitatively, how the parameters that control the shape of the coupling kernel, coupling strength, and aspects of spatially-smoothed space-time noise, influence the pattern in the resulting evolving random field. We confirm that a spatial pattern that is damped in time in a deterministic system may be sustained and amplified by stochasticity. We find that spatially-smoothed noise alone causes pattern formation even without direct spatial coupling. Our analysis of the interaction between coupling and noise sharing allows us to determine parameter combinations that are optimal for the formation of spatial pattern.

Canadian Journal of Psychology/Revue canadienne de psychologie

The Behavioral and brain sciences, 2016

We expand upon Morsella et al.'s synthesis in the direction of what Gibson (1979) called an e... more We expand upon Morsella et al.'s synthesis in the direction of what Gibson (1979) called an ecological approach to perception. Morsella et al. describe consciousness as a director of voluntary action, but they understate the role of the environment in its evolution as well as in directing behavior. We elaborate these roles in the context of the concept of affordances.

Journal of Experimental Psychology General, 1990

It is well known that, although psychophysical scaling produces good qualitative agreement betwee... more It is well known that, although psychophysical scaling produces good qualitative agreement between experiments using ostensively the same methods but run in different laboratories, quantitative agreement is much more difficult to achieve. Constrained scaling, in which observers first learn a standard scale and then make magnitude judgments of other stimuli using the learned scale, has achieved excellent quantitative agreement between individual observers' psychophysical functions and could theoretically do the same for across-laboratory comparisons. We report two experiments that were replicated, using constrained scaling, in two different laboratories as examples of the level of agreement achievable with this technique. In general, we found acrosslaboratory agreement superior to that typically obtained with magnitude estimation.

Annual Review of Psychology

Encyclopedia of Perception, 2010

Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2013

Information processing in nonlinear systems can sometimes be enhanced by the presence of stochast... more Information processing in nonlinear systems can sometimes be enhanced by the presence of stochastic fluctuations, or noise. Although the electrical properties of neurons and synapses are known to be influenced by intrinsic stochastic variability, it remains an open question as to whether living systems exploit this noise during neuronal information processing. This is despite various forms of noise-enhanced processing, such as classical stochastic resonance, having been observed in mathematical models of neural systems and in data acquired experimentally. We recently argued that advancing our understanding of the potential roles of random noise in assisting neuronal information processing will require specific focus on a concrete hypothesis about the computational roles of a specific neural system that can then be tested experimentally using signals and metrics relevant to the hypothesis. In this invited symposium paper, we argue why most existing approaches to studying stochastic r...

The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 2003

Recently there has been indirect evidence suggesting that age-related elevation in footsole vibra... more Recently there has been indirect evidence suggesting that age-related elevation in footsole vibration detection may be associated with balance and gait dysfunction. As a first step in investigating this dysfunction, the current study determined by how much plantar vibration sensation decreases as a function of age, and if change is dependent on frequency and location of vibration application. Vibration thresholds were assessed at 4 frequencies (25-400 Hz), at 55 locations, and in young and older participants. Results showed there were 3 regions of sensitivity on the footsole: the ball/medial arch, the lateral border of the foot and heel, and the toes. Thresholds for fast-adapting type I receptor (FAI)-mediated frequencies were age invariant; however, thresholds for fast-adapting type II receptor (FAII)-mediated frequencies increased with age. These changes may be one of many factors contributing to age-related changes in gait.

Europhysics Letters (EPL), 2007

We demonstrate that both detection of weak visual signals to the right eye and phase synchronizat... more We demonstrate that both detection of weak visual signals to the right eye and phase synchronization of electro-encephalogram (EEG) signals from widely separated areas of the human brain are increased by addition of weak visual noise to the left eye. We found a close relationship between the resulting noise-induced changes in behavioural performance and the similarly resulting changes in phase

Behavioral and Brain Sciences, 1993